Apparatus for reducing a temperature gradient of mainstream fluid downstream of an airfoil in a gas turbine engine

ABSTRACT

An apparatus ( 100 ) is presented for reducing a temperature gradient ( 30 ) of mainstream fluid ( 118 ) downstream of an airfoil ( 112 ) in a gas turbine engine ( 110 ). The apparatus includes a passage ( 116 ) in a trailing edge ( 114 ) of the airfoil having an inlet ( 132 ) and an outlet ( 134 ). The apparatus also includes a cooling fluid source ( 136 ) coupled to the inlet to transmit cooling fluid into the passage. The apparatus also includes a vortex generator ( 138 ) within the passage effective to generate a vortex fluid ( 140 ) at the outlet. The outlet is positioned to inject the vortex fluid into the mainstream fluid with sufficient mixing energy to cause a reduced temperature gradient ( 130 ) downstream of the airfoil.

FIELD OF THE INVENTION

Aspects of the invention are related to turbo machines, and more particularly, to a mainstream fluid flow within a turbo machine.

BACKGROUND OF THE INVENTION

In a gas turbine engine power generating machine, fluid is initially compressed by a compressor, is subsequently heated in a combustion chamber, and the mainstream fluid so produced passes to a turbine that, driven by the mainstream fluid, does work which may include rotating the compressor. The temperature of the mainstream fluid in the turbine typically exceeds the melting point of most turbine components, including stationary airfoils and rotating blades. Thus, cooling fluid is routinely passed through an interior of these turbine components, before the cooling fluid is ejected into the mainstream fluid. As a result of ejecting the relatively cooler cooling fluid from a turbine component into the relatively hotter mainstream fluid, downstream turbine components are subjected to a temperature gradient.

FIG. 1 illustrates a conventional gas turbine engine 10 with an airfoil 12 having a trailing edge 14. A passage 16 is formed in the trailing edge 14, to eject the cooling fluid 20 into the mainstream fluid 18 after the cooling fluid 20 has passed through the interior of the airfoil 12. FIG. 1 illustrates a temperature profile 28 downstream of the airfoil 12, along a tangential direction between a centerline 22 and a pair of lateral edges 25, 27 of the temperature profile 28. The lateral edges 25, 27 of the temperature profile 28 depict the downstream lateral edges of shear layer intersections 29, 31 between the cooling fluid 20 and the mainstream fluid 18, as projected from the lateral edges 24, 26 of trailing edge 14. The temperature profile 28 shows a steep gradient 30 between the centerline 22 and the lateral edges 25, 27. As appreciated by one skilled in the art, the steep temperature gradient 30 experienced by downstream turbine components can cause unwanted stress gradients in these components and reduce their useful life.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is explained in the following description in view of the drawings that show:

FIG. 1 is a view of a temperature profile downstream of a conventional airfoil in a gas turbine engine;

FIG. 2 is a cross-sectional side view of an airfoil in a gas turbine engine;

FIG. 3 is a partial cross-sectional top view of a trailing edge of the airfoil of FIG. 2;

FIG. 4 is a view of a temperature profile downstream of the airfoil of FIG. 2;

FIG. 5 is a cross-sectional view of an outlet of the trailing edge of FIG. 3;

FIG. 6 is a cross-sectional view of an alternative outlet of the trailing edge of FIG. 3; and

FIG. 7 is a partial cross-sectional top view of an alternate trailing edge of the airfoil of FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

The present inventor has recognized several limitations of the conventional approaches used for ejecting cooling fluid from a cooled airfoil of a gas turbine engine. The inventor has recognized that downstream mixing of the cooling fluid from the airfoil with the mainstream fluid is limited, resulting in the temperature gradient downstream of the airfoil, and that these limitations arise due to insufficient vorticity between the cooling fluid and the mainstream fluid upon ejecting the cooling fluid from the airfoil into the mainstream fluid. Thus, the present inventor has recognized that a more effective approach would involve initiating a vorticity between the cooling fluid and the mainstream fluid upon ejecting the cooling fluid from the airfoil into the mainstream fluid.

Additionally, the present inventor has recognized that while the conventional airfoil trailing edge arrangement does introduce cooling fluid into the mainstream fluid path from outside of the mainstream fluid path, the introduced cooling fluid has linear momentum which lacks the necessary vorticity to significantly mix the mainstream fluid adjacent to the airfoil trailing edge with the cooling fluid and thereby reduce the temperature gradient downstream of the airfoil. Accordingly, the present inventor has designed an apparatus which introduces cooling fluid into the mainstream fluid path with a necessary vorticity to significantly mix the mainstream fluid with the cooling fluid and thereby to reduce the temperature gradient downstream of the airfoil.

FIG. 2 illustrates an apparatus 100 for reducing a temperature gradient of mainstream fluid downstream of an airfoil 112 in a gas turbine engine 110. A compressor (not shown) of the gas turbine engine 110 initially compresses fluid, which is subsequently heated by a combustion chamber to produce mainstream fluid 118 (FIG. 3) that is passed into the turbine. In an exemplary embodiment, the airfoil 112 is a stationary or rotating airfoil within the turbine section of the gas turbine engine 110.

However, the embodiments of the present invention are not limited to airfoils used within the turbine section of a gas turbine engine, and may be used to reduce downstream temperature gradients of any airfoil used in a turbo machine.

As illustrated in FIG. 2, the airfoil 112 includes a root section 139 and an airfoil section 115 with a trailing edge 114 that is connected to the root section 139. The airfoil 112 also includes a cooling fluid passage 116 in the trailing edge 114. Cooling fluid is passed through an inlet 137 in the root section 139 of the airfoil 112, and internal passages 136 form a serpentine network within the airfoil 112 to direct the cooling fluid within an interior of the airfoil 112. FIG. 3 illustrates that the passage 116 includes an inlet 132 to receive the cooling fluid from the internal passages 136 of the airfoil 112. Although FIG. 3 illustrates that the passage inlet 132 receives the cooling fluid from the internal passages 136 within the airfoil 112, any cooling fluid source may be used to transmit cooling fluid into the inlet 132 of the passage 116. As illustrated in FIG. 3, the passage 116 also includes an outlet 134 to eject the cooling fluid from the airfoil 112 and into the mainstream fluid 118 of the gas turbine engine 110.

FIG. 3 further illustrates that the apparatus 100 includes a vortex generator 138 positioned within the passage 116 and is effective to generate a vortex fluid 140 at the outlet 134 of the airfoil 112. In the exemplary embodiment of FIG. 3, the vortex generator 138 is a swirler that is positioned within the passage outlet 134, and includes a solid spiral-shaped piece positioned and mounted within the passage 116, to impart vorticity into the vortex fluid 140 at the outlet 134. In an exemplary embodiment, the passage 116 may be a conventional cooling hole in the trailing edge 114, for ejecting cooling fluid after the cooling fluid is passed through the serpentine network of the internal passages 136. Although the embodiment of FIG. 3 illustrates one swirler within the passage 116, more than one swirler may be positioned within the passage 116, depending on the desired vorticity pattern in the vortex fluid 140. As illustrated in FIG. 3, the vortex generator 138 extends a length 145 into the passage 116 from the outlet 134, and the passage 116 has a length 147. Although FIG. 3 illustrates that the vortex generator 138 is positioned at the outlet 134 of the passage 116, the embodiments of the present invention are not limited to this arrangement and the vortex generator 138 may be positioned at any location along the length 147 of the passage 116, provided that the vortex fluid 140 is generated at the outlet 134.

As illustrated in FIG. 4, the vortex fluid 140 has a vorticity such that upon injecting the vortex fluid 140 into the mainstream fluid 118, the vortex fluid 140 is mixed with the mainstream fluid 118. The vorticity of the vortex fluid 140 is based on one or more parameters of the vortex generator 138, which is discussed in greater detail below. FIG. 4 illustrates a downstream temperature profile 128 from the airfoil 112, between a centerline 122 and lateral edges 125, 127 of temperature profile 128. Lateral edges 125, 127 depict the downstream lateral edges of shear layer intersections 129, 131 between the vortex fluid 140 and the mainstream fluid 118, as projected from the lateral edges 124, 126 of trailing edge 114. The temperature profile 128 features a reduced temperature gradient 130, relative to the steep temperature gradient 30 of the conventional temperature profile 28 in the conventional gas turbine engine 10 of FIG. 1. The injected vortex fluid 140 mixes the mainstream fluid 118 with the vortex fluid 140, in order to transfer thermal energy from the mainstream fluid 118 to the vortex fluid 140, and thereby reduce the downstream temperature gradient 30 to that of a reduced temperature gradient 130. By transferring thermal energy from the mainstream fluid 118 adjacent to the trailing edge 114 to the vortex fluid 140, the reduced temperature gradient 130 is minimized. Effectively, the injected vortex fluid 140 strengthens embedded vortices (not shown) within the shear layer intersection regions 129, 131, which improves mixing between the mainstream fluid 118 and the vortex fluid 140.

The inventor of the present invention recognized that in order for the vortex fluid 140 to effectively mix the mainstream fluid 118 adjacent to the trailing edge 114, the vorticity of the vortex fluid 140 should be capable of reaching from the outlet 134 of the trailing edge 114 to the mainstream fluid 118 adjacent to the trailing edge 114. Thus, as illustrated in FIG. 4, the vortex generator 138 is configured such that the generated vortex structure of the vortex fluid 140 has a diameter which is greater than the distance between the lateral edges 124, 126 of the airfoil 112. The vortex fluid 140 can then reach from the centerline 122 at the outlet 134 of the trailing edge 114 to the mainstream fluid 118 and effectively mix and transfer thermal energy from the mainstream fluid 118 to the vortex fluid 140. Although the exemplary embodiment of FIG. 3 illustrates the vortex generator 138 within the passage 116, the embodiments of the present invention need not include a structural vortex generator positioned within the passage, provided that the passage is capable of generating a vortex fluid at the outlet.

Although the exemplary embodiment of FIG. 3 illustrates that the vortex generator 138 is a swirler inserted within the outlet 134, other embodiments of the present invention provide alternative vortex generators which may be employed to impart vorticity into the vortex fluid 140. For example, FIG. 5 illustrates a cross-sectional end view of the outlet 134 with an alternative vortex generator 138′ that includes a plurality of swirler channels 144′ within the passage 116. The swirler channels 144′ are positioned in an outer portion 146′ at an outer radial portion of the outlet 134. The swirler channels 144′ are cast using a microfabrication casting technique which may be used to cast the vortex generator 138′ as an insert to be positioned within the outlet 134 of the passage 116. In an exemplary embodiment, the microfabrication casting technique may be employed for purposes of the relatively small dimensions of the swirler channels 144′ compared to the relatively large dimensions of the airfoil 112, and to finely tune the precise curvature of the swirler channels 144′ using swirlers during the casting process, for example. In an exemplary embodiment, after the microfabrication casting technique has been utilized to cast the swirler channels 144′ of the vortex generator 138′, the vortex generator 138′ may be inserted within the outlet 134 of a conventionally cast or drilled passage 116, for example. Alternatively, the microfabrication casting technique could be integral with the casting of airfoil 112. As illustrated in FIG. 5, the vortex generator 138′ further comprises a solid core 148′ within a central portion 150′ of the passage 116. The central portion 150′ is located at an inner radial portion of the outlet 134, in contrast with the outer portion 146′ at an outer radial portion of the outlet 134. The swirler channels 144′ are disposed about the solid core 148′ such that the solid core 148′ redirects cooling fluid from the central portion 150′ into the swirler channels 144′, to generate increased vorticity in the vortex fluid 140 exiting the outlet 134.

In another example, FIG. 6 illustrates a cross-sectional end view of the outlet 134 with an alternative vortex generator 138″ that is similar to the vortex generator 138′ of FIG. 5 but includes a hollow core 148″ rather than the solid core 148′ within the central portion 150″ of the passage 116. The swirler channels 144′ are disposed about the hollow core 148″ in the same manner as the swirler channels 144′ are disposed about the solid core 148′ in the vortex generator 138′ of FIG. 5. During operation of the vortex generator 138″, fluid within the swirler channels 144′ will tend to entrain fluid from the hollow core 148″ along with the fluid within the swirler channels 144′, which increases the vorticity of the fluid within the hollow core 148″, and thus improves the vortex structure of vortex fluid 140 at the outlet 134.

The vorticity generated by the swirler channels of FIGS. 5 and 6 or the swirler of FIG. 3 is based on various characteristics of the swirler channels or swirler, such as a turn radius of the swirler channel/swirler, and/or a number of rotations per unit length of the swirler channels/swirler. For example, an increased number of rotations per unit length of the swirler channels/swirler of the vortex generator may improve the vorticity of the vortex fluid. Although FIGS. 5 and 6 illustrate that the outlet 134 of the passage 116 would be circular, the outlet need not be circular, and may take any shape, provided that the ejected vortex fluid is capable of adequately mixing the mainstream fluid with the vortex fluid in order to reduce the downstream temperature gradient.

Although the above embodiments of the apparatus 100 discuss using a vortex generator within the passage 116 of the trailing edge 114 to generate the vortex fluid 140 at the outlet 134 of the passage 116, an alternative apparatus 100′ may be provided with similar vortex generator features which enhance the mixing between the vortex fluid 140 and the mainstream fluid 118. For example, as illustrated in FIG. 7, in addition to positioning the vortex generator 138 within the passage 116′ at the outlet 134′, the passage 116′ may be oriented at an angle with respect to the centerline 122 and the direction of flow of the mainstream fluid 118 outside of the airfoil 112. Regardless of the orientation of the outlet 134′ with respect to the direction of flow of the mainstream fluid 118, the injected vortex fluid 140′ strengthens embedded vortices (not shown) within the shear layer intersection regions (not shown), which improves mixing between the mainstream 118 and the vortex fluid 140′.

The exemplary embodiment of FIG. 2 shows multiple vortex generators 138 along the trailing edge 114 of the airfoil 112. Adjacent vortex generators 138 can be configured such that adjacent vortex fluids 140, shown in FIG. 3, have vorticity in the same direction as each other, or alternatively configured such that adjacent vortex fluids have vorticity in the opposite direction as each other in order to enhance the strengthening of embedded vortices within the shear layer interaction region.

While various embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions may be made without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims. 

The invention claimed is:
 1. An airfoil of a gas turbine engine comprising: a root section; an airfoil section comprising a trailing edge connected to the root section; a cooling fluid passage in the trailing edge; and a vortex generator within the trailing edge cooling fluid passage effective to generate vorticity in cooling fluid that is ejected from the passage.
 2. The airfoil of claim 1, wherein the vorticity is effective to reduce a temperature gradient downstream of the airfoil.
 3. The airfoil of claim 1, wherein the vortex generator comprises a swirler inserted within an outlet of the passage.
 4. The airfoil of claim 1, wherein the vortex generator comprises a plurality of swirler channels within the passage, and wherein said swirler channels are positioned in an outer portion of the passage.
 5. The airfoil of claim 4, wherein the vortex generator further comprises a solid core within a central portion of the passage, wherein the swirler channels are disposed about the solid core such that said solid core is configured to redirect fluid from the central portion into the swirler channels.
 6. The airfoil of claim 4, wherein the vortex generator further comprises a hollow core within a central portion of the passage, and wherein the swirler channels are disposed about the hollow core.
 7. The airfoil of claim 1, further comprising a plurality of cooling fluid passages in the trailing edge and a respective vortex generator in each passage, wherein adjacent vortex generators are configured to rotate the cooling fluid from adjacent passage outlets with a vorticity in opposite directions.
 8. An airfoil for a gas turbine engine wherein an improvement comprises: a passage in a trailing edge of the airfoil, said passage including an inlet and an outlet, said passage configured to receive cooling fluid in the inlet and further configured to generate a vortex fluid at the outlet; wherein when said vortex fluid is injected into a mainstream fluid passing over the airfoil, the vortex fluid will mix with the mainstream fluid.
 9. The airfoil of claim 8, wherein the passage is configured such that the injected vortex fluid will mix with the mainstream fluid such that a temperature gradient of the mainstream fluid is reduced downstream of the airfoil.
 10. The airfoil of claim 8, wherein said passage is configured to receive the cooling fluid from a serpentine cooling fluid network of the airfoil positioned upstream in the cooling fluid from the passage in the trailing edge.
 11. The airfoil of claim 8, wherein said passage includes at least one swirler channel configured to generate a vorticity of the vortex fluid to be injected from the outlet into the mainstream fluid.
 12. An airfoil for injecting a vortex fluid into a mainstream fluid passing over the airfoil, said airfoil comprising: a trailing edge of the airfoil; and a vortex generator having an outlet in the trailing edge for injecting the vortex fluid into the mainstream fluid.
 13. The airfoil of claim 12, wherein a plurality of outlets in the trailing edge and a respective vortex generator in each outlet are configured to generate a respective vortex fluid exiting each outlet, wherein the adjacent vortex generators are configured to rotate the vortex fluid from adjacent outlets with a vorticity in a same direction.
 14. The airfoil of claim 12, wherein a plurality of outlets in the trailing edge and a respective vortex generator in each outlet are configured to generate a respective vortex fluid exiting each outlet, wherein the adjacent vortex generators are configured to rotate the vortex fluid from adjacent outlets with a vorticity in an opposite direction.
 15. The airfoil of claim 12, further comprising a passage within the trailing edge, wherein said vortex generator is positioned within the passage, wherein said vortex generator includes at least one swirler channel to generate the vortex fluid at the outlet and wherein said vortex fluid is effective to generate a secondary vorticity in the mainstream fluid.
 16. The airfoil of claim 15, wherein the vortex generator further comprises a solid core within a central portion of the passage, and wherein the vortex generator includes a plurality of swirler channels disposed about the solid core such that said solid core is configured to redirect fluid from the central portion into the swirler channels to generate the vortex in the cooling fluid exiting the outlet.
 17. The airfoil of claim 15, wherein the vortex generator further comprises a hollow core within a central portion of the passage, wherein the vortex generator further comprises a plurality of swirler channels, and wherein the swirler channels are disposed about the hollow core. 